What does HIGH AN SENSOR or LOW AN SENSOR mean on a Sullair STS?
Short answer: Analog sensor circuit open or shorted. If your Sullair Touch Screen (STS) is showing HIGH AN_ SENSOR / LOW AN_ SENSOR, the controller has logged a specific, documented condition. This page covers what it means, what causes it, what you can safely fix yourself, and when — and why — it takes a technician.
What exactly is the machine telling you?
A device on the indicated analog input (pressure transducer, temperature probe, etc.) or its wiring has failed — HIGH indicates an open circuit, LOW a short. The compressor shuts down because the controller can no longer trust that reading.
Which machines show this?
current-generation Sullair stationary rotary screw compressors — the LS-series and related packages built from the late 2010s onward — fitted with the 10-inch Sullair Touch Screen (STS) controller. The STS spells out problems as plain-English named faults and warnings ('High Temperature 1', 'Failed to Unload', 'Replace I/O Battery') rather than bare code numbers, and pairs them with live readings and a Recommended Service screen that tracks filter and separator hours. Warnings keep the machine running; faults shut it down until reset. Practical tip: before clearing anything, photograph the fault screen and the Recommended Service page — the service-hour counters usually point straight at the consumable that caused the trip.
What causes it?
- Open circuit (HIGH) or short (LOW) in the named analog sensor or its wiring
- A failed transducer or temperature probe
- A momentary loose connection
Can you fix it yourself?
Sometimes — with power locked out, check the connector and look for chafed wiring, then reset once.
Step by step — what to try, in order:
- With power locked out, visually check that the sensor connector is plugged in and undamaged
- Look for chafed or pinched sensor wiring
- Reset and restart once to rule out a momentary connection issue
When do you need a technician — and why?
If it returns, the transducer or probe needs meter testing and the correct replacement part — sensor diagnosis, not parts-cannon guessing.
If it does come to a service call and you're in Nashville, TN or Birmingham, AL, we maintain independently compiled lists of local companies that service industrial air compressors — real businesses with verified contact information, none of whom paid to be listed.
Related questions
What does HIGH AN_ SENSOR / LOW AN_ SENSOR mean on a Sullair Touch Screen (STS)?
Analog sensor circuit open or shorted. A device on the indicated analog input (pressure transducer, temperature probe, etc.) or its wiring has failed — HIGH indicates an open circuit, LOW a short. The compressor shuts down because the controller can no longer trust that reading.
Can I fix HIGH AN_ SENSOR / LOW AN_ SENSOR on a Sullair Touch Screen (STS) myself?
Sometimes — with power locked out, check the connector and look for chafed wiring, then reset once.
When does HIGH AN_ SENSOR / LOW AN_ SENSOR on a Sullair Touch Screen (STS) need a technician?
If it returns, the transducer or probe needs meter testing and the correct replacement part — sensor diagnosis, not parts-cannon guessing. Call a technician to test and replace the transducer or probe if the fault returns — sensor diagnosis requires a meter and the correct replacement part.
Verified against service documentation: Sullair Touch Screen (STS) documentation for HIGH AN_ SENSOR / LOW AN_ SENSOR (sullair.com)